Table of Contents
Severity: Medium
You have selected to use the ZIP archive format, but JoomlaPack is unable to reliably calculate the CRC checksums. The reason can be:
You still use PHP 4 or, generally, PHP with a version lower than 5.1.2
You have PHP 5.1.2 or greater, but the "hash" extension is not present or activated in your php.ini
You have PHP 5.1.2 or greater, but the functionality of the "hash" extension is blocked by your host
Under these circumstances, a seemingly broken ZIP archive can be produced by JoomlaPack. More specifically, on files larger than roughly 1Mb JoomlaPack won't be able to calculate the CRC checksum and instead use the dummy 0x00000000 checksum. As a result, archiving software (including, but not limited to, WinZIP, WinRAR, 7-Zip, Ark, File-Roller, Windows Compressed Folder etc.) will think the archive is damaged and skip extraction of these files. The partially extracted backup set won't restore correctly.
Moreover, the CRC calculation code JoomlaPack uses when the "hash" extension is not present is much more resource intensive (by one to tow orders of magnitude, compared to the "hash" extension!) and has thus the potential of causing the archiving process to fail with a timeout, especially on overloaded or slow servers.
Depending on the source of the problem, you can try several workarounds:
Some archivers offer an option to ignore CRC errors, so you can use it to extract afflicted archives.
Switch to the latest PHP 5 build; after all, newest versions incorporate security-related bug fixes
Download the PHP "hash" extension and / or enable it on your server
Remove any limitations regarding the "hash" extension (e.g. by editing disabled_functions in your php.ini)
Use the JPA Archive Format, the renowned archive format of JoomlaPack which is much more efficient during archiving and extraction.
JoomlaPack detects potential issues which might negatively impact the backup process. Many of them are caused by specific PHP configurations. The cause of those issues is mostly or thoroughly known, but since it resides in the server configuration which JoomlaPack can not control we can't provide some "patch" or bug fix to solve them. We try to provide practical solutions or workarounds instead.
The severity of each of these warnings is displayed on the top of this help screen. There are three levels: low, medium and high. The "Low" level implies that the detected issue will most probably have no impact on you. "Medium" level warnings have a higher chance of causing problems, but the proposed workaround may be applied to alleviate its effects. "High" level warnings should be treated as errors; the detected issue will cause backup failure unless the proposed workaround is applied.
Remember, if all else fails, contact us on our support forum . We are here to help you. Please, before posting to the forum, try to follow the "workaround" procedure outlined above and tell us that you did try the proposed solution before asking us for support.